From: Sean Bright <sean@seanbright.com>
Date: Sat, 17 Feb 2024 19:41:38 +0000 (-0500)
Subject: strings.h: Ensure ast_str_buffer(…) returns a 0 terminated string.
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=31ab82840b031b17643adf742b84cd2ed6924df2;p=thirdparty%2Fasterisk.git

strings.h: Ensure ast_str_buffer(…) returns a 0 terminated string.

If a dynamic string is created with an initial length of 0,
`ast_str_buffer(…)` will return an invalid pointer.

This was a secondary discovery when fixing #65.
---

diff --git a/include/asterisk/strings.h b/include/asterisk/strings.h
index 10eb011463..935c7e9236 100644
--- a/include/asterisk/strings.h
+++ b/include/asterisk/strings.h
@@ -753,7 +753,10 @@ char * attribute_pure ast_str_buffer(const struct ast_str *buf),
 	 * being returned; eventually, it should become truly const
 	 * and only be modified via accessor functions
 	 */
-	return (char *) buf->__AST_STR_STR;
+	if (__builtin_expect(buf->__AST_STR_LEN > 0, 1)) {
+		return (char *) buf->__AST_STR_STR;
+	}
+	return "";
 }
 )